System and method for treating infectious waste matter

ABSTRACT

In accordance with the present invention, a system and method is provided for producing a safely disposable end product from waste matter containing undesirable materials, such as infectious, biohazardous, hazardous, or radioactive elements. The method comprises the steps of providing a highly basic solvent, immersing the waste matter containing the undesirable materials within the highly basic solvent, and heating the solvent. The waste matter containing the undesirable materials is allowed to remain within the solvent until digested, thereby forming a solution void of any infectious or biohazardous elements and/or containing a concentration of radioisotope below the maximum permissible concentration (MPC) for release to a sanitary sewer as defined in applicable federal regulations. The invention further provides a system for producing a safely disposable end product void of any infectious or biohazardous elements and/or containing only a concentration of radioisotope below the MPC for release to a sanitary sewer as defined in applicable federal regulations from waste matter containing such materials. The system comprises a tank or vessel capable of containing a highly basic solvent during a closed digestion reaction, heating means for heating the solvent within the vessel, filtering means, and means for removing the post-digestion aqueous solution and solid waste materials from within the vessel. The post-digestion product in both aqueous and solid form can then by disposed of by conventional means.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority on PCT application Serial No.PCT/US01/02319, filed Jan. 24, 2001 and U.S. provisional patentapplication Ser. No. 60/178,051, filed Jan. 24, 2001. This applicationis also related to U.S. patent application Ser. No. 09/171,447, filedOct. 20, 1998, titled “Methods for Treatment and Regulated MedicalWaste,” which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to the field of waste disposal and, moreparticularly, to a system and method for the digestion and sanitarydisposal of infectious waste material and other biohazardous orradioactive waste.

BACKGROUND OF THE ART

Many facilities, such as hospitals, various health-care facilities,research and teaching institutions, food preparation facilities, and thelike, produce considerable amounts of infectious, biohazardous, orradioactive waste. Such waste may include surgical and pathologicaltissues, animal tissues, cadavers, blood and other bodily fluids,disposable matter exposed to blood, and other potentially infectious ordangerous body fluids of patients or animals. Such waste is classifiedin the United States as “regulated medical waste” (RMW) under stateregulations, and must be disposed of in strict compliance with theapplicable governmental regulations.

Health-related organizations and governmental regulatory agencies havebecome increasingly concerned with the adequacy of existing cleaning anddisposal methods. It has been discovered that some potentiallybiohazardous agents, such as prokaryotes, or infective proteins (prions)do in fact survive standard autoclaving procedures. Thus, more effectivesterilization techniques have been sought for treating solid infectiousbiomedical waste and aqueous solutions containing such waste.

In addition, universities and other research facilities likewise producesignificant amounts of such waste. For example, in conductingexperiments in cell lines, tissues, or animals, it is common tointroduce dyes, toxic chemicals, or infectious agents into the testsubject. Moreover, radioactive materials are also commonly used as atool to enhance chemical, biochemical, pharmaceutical, biomedical, andbiological research. It is common to label drugs or chemical compoundswith radioisotopes in order to study efficiently and accurately wherethese compounds are metabolized and incorporated within the body. Aftercompletion of the test and analysis, due to the introduction ofinfectious agents or hazardous or radioactive material into the tissue,the remaining tissue or animal carcass may fall under the classificationof “regulated medical waste,” hazardous waste, or low-level radioactivewaste (“LLRW”). In addition, animal waste, animal bedding, handlingmaterials, and other matter exposed to any animal body fluids orexcretions may also need to be treated as infectious or hazardous wastematerial, thus requiring disposal in accordance with the applicablegovernmental regulations.

Moreover, it is common today for health care organizations to cleanmaterial, instruments or surface areas exposed to infectious agents,including zoonotic agents, with disinfectants such as formaldehyde orglutaraldehyde. Spent cleaning solution is considered hazardous liquidwaste and must also be disposed of in compliance with governmentalregulations. The cost of disposing of such waste, on an institutionalbasis, can be quite high. Further, formaldehyde, glutaradehyde, phenolsand like materials, are commonly used for embalming tissues and infixation of infectious biological materials. Thus, these tissues and thefixative agents may also have to be disposed of as “regulated medicalwaste,” hazardous waste, or mixed waste in compliance with theapplicable governmental regulations.

Further, animal carcasses containing compounds labeled with ¹⁴C or ³H orother radioisotopes are classified as LLRW. Because state and federalguidelines regulate the disposal of LLRW, special precautions must befollowed in their disposal. Currently, the two methods commonly used indisposing of this type of waste are incineration and land burial.Presently, federal law allows for incineration only when the animalcarcass contains a radioisotope concentration below a certain level.However, even when radioisotope concentrations are below this level,incineration may be further limited by state and local agencies. Whenthe levels of radioactivity in the animal carcasses are below acceptablede minimis levels as defined by federal, state, and local authorities,the disposal thereof is not subject to any additional regulation as aradioactive waste. However, to further complicate matters, theincineration of radioactive animal carcasses at any level is prohibitedin certain major metropolitan areas. Nonetheless, the general process ofincineration itself, even when no radioactive materials are involved, issubject to additional regulations, such as those requiring licensingfrom a state or local environmental agency. Additionally, futureincreases in the requirements for incinerator designs and function underclean air regulations put in doubt the continued availability ofincineration as a practical method for disposing of animal carcassesclassified as LLRW or for any non-radioactive carcasses or humanpathological waste.

Presently, the only real alternative to incineration for radioactiveanimal carcasses is burying the carcasses in a licensed LLRW disposalfacility. This method entails the packing of the entire carcasses inlime and adsorbents, repacking them in special drums and shipping thedrums to a LLRW site. Currently there are only two such sites in theUnited States, located at Hanford, Wash., and Banwell, S.C. Due to thelimited number of land burial sites currently operating in the UnitedStates, it is extremely costly to dispose of any radioactive waste bythis method; it is disproportionately costly for animal carcassescontaining low level radioactive waste due to the size and weight of thecarcass. Due to the extremely high cost associated with land burial andthe limitations on access to current sites, the feasibility of landburial as a method of disposing of animal carcasses classified as LLRWremains in doubt.

It is known in the art that low levels of certain radioactive waste maybe disposed of to a sanitary sewer under federal regulations withappropriate record keeping and/or monitoring. This includes isotopes inaqueous solution at levels below the maximum permissible concentration(MPC) as defined by 10 C.F.R. 20 and radioisotopes in human waste. Sucha procedure has been utilized, for example, in the disposal ofradioactive waste generated by many patients undergoing treatments forcancer. Today, a common method of treating cancer is by radiationtherapy, which often involves the absorption of radioactive compounds.Many of these radioactive compounds eventually leave the body throughfecal and urinary excretions. These excretions will contain smallamounts of radioactive material. However, this radioactive material isdisposed of through the general sewage system because the level of theradioactive materials discharged by the body into the sewer system issufficiently diluted such that it no longer poses any hazard to publichealth and safety. This process is well within the state and federaldisposal regulations for LLRW disposal. However, LLRW contained inanimal remains are not readily capable of disposal through such meansbecause the animals are naturally solid waste.

It is also known in the art that substances containing keratin, such ashair and nails, may be dissolved by means of acid or alkalinehydrolysis, as disclosed in U.S. Pat. No. 1,974,554 issued to Ziegler.It is further known that hydrolysis of proteins containing keratin maybe carried out with alkaline solvents. It is even further disclosed inU.S. Pat. No. 5,332,532 to Drs. Kaye and Weber, which patent is commonlyowned by the assignee of the present application, that such hydrolysismay be utilized on proteins contaminated with radioactive materials.

Of the known methods of disposing of infectious, biohazardous, orlow-level radioactive waste, each faces an indeterminable future underthe ever-changing breadth of the environmental laws. Furthermore, eachis extremely costly, putting an unneeded drain on already strainedresearch and waste management budgets of hospitals, universities andother institutions. Thus, a need persists for means of safely andinexpensively treating waste matter containing infectious, biohazardous,or radioactive materials, and for the safe and convenient disposal ofthe resultant aqueous and solid waste materials.

SUMMARY OF INVENTION

This need is satisfied and the limitations and expenses of the prior artare overcome, in accordance with the principles of the presentinvention, by providing a system and method for producing a safelydisposable solution and solid waste from infectious or biohazardoushuman or animal tissue, regulated medical waste, or any other materialcontaining undesirable elements. This invention provides a system forproducing a safely disposable sterile solution and sterile solid waste,comprising a sealable tank or vessel capable of containing a highlybasic solvent therein, heating means for heating the highly basicsolvent, filtering means, means for removing the odor created by suchactivities, means for removing the post-digestion resultant aqueoussolution and any solid waste from within the vessel, and means fordisposing of the resultant aqueous and/or solid waste via conventionalmeans.

The method provided by the invention generally comprises the steps ofproviding a sealable vessel, filling the vessel with a highly basicsolvent, immersing the waste matter containing the undesirable elementswithin the highly basic solvent, and heating the highly basic solvent.The waste matter is allowed to remain within the highly basic solventuntil the hydrolyzable matter is digested, thereby forming a sterilesolution and sterile solid waste. The aqueous solution and any resultantsolid waste may then be disposed of through conventional means, such asa sanitary sewer or local landfill facility.

In another aspect of the invention, hazardous materials may be removedfrom the digest and separately disposed of in an appropriate manner,such as a specially designated landfill or an incineration facility.Paraffin or wax may be added to the RMW prior to or subsequent to thedigestion cycle. Upon heating the materials, the paraffin or wax meltsand becomes distributed through the aqueous solution. After the wastehas been digested and the aqueous solution allowed to cool, thelipid-like materials separate out from and float to the surface of thesolution where they re-solidify upon cooling to room temperature. Lipidsoluble waste materials may then be removed from the aqueous phase uponseparation of the lipid phase because they have become incorporatedwithin the lipid phase. Thus, removing the lipid phase from the solutioneffectively removes lipid soluble hazardous materials not degraded orotherwise consumed in the alkaline treatment as well.

As used herein, “regulated medical waste” shall mean any wastepotentially containing infectious agents that can cause infection inhumans or animals. Such regulated medical waste includes but is notlimited to tissues (human or animal), cloth, plastic, paper, animalcarcasses, bedding and other matter potentially containing infectious orbiohazardous agents.

Accordingly, it is an object of this invention to provide a system andmethod for safely treating and disposing of waste matter containingundesirable elements, such as infectious, biohazardous, hazardous, orradioactive elements or agents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the system provided by acurrently preferred embodiment of the invention;

FIG. 2 is a flowchart representation of the method provided by acurrently preferred embodiment of the invention;

FIGS. 3A, 3B and 3C are side, top and bottom elevations, respectively,of a holding container for receiving and storing the waste matter withinthe vessel chamber interior during the digestion cycle;

FIG. 4A shows an exploded elevation of a unique vacuum balancer deviceprovided by the invention;

FIGS. 4B and 4C show the vacuum balancer of FIG. 4A in its open andclosed states, respectively; and

FIGS. 5A-5D show various views of agitating injector means provided bythis invention.

BEST MODE FOR CARRYING OUT THE INVENTION

This invention involves a system and method for treating and safelydisposing of waste matter containing undesirable agents or elements,such as but not limited to infectious, biohazardous, hazardous, andradioactive materials. The system and method of this invention isdesigned and intended to comply with all federal, state, and local lawsor regulations presently in existence applicable to the disposal of suchwaste.

The method of the invention comprises the steps of providing a sealablevessel, providing a highly basic solvent, immersing the waste mattercontaining the undesirable elements within the solvent within theinterior of the vessel, heating the solvent and the waste matter, andallowing the waste matter to remain within the solvent until digested,thereby forming a sterile aqueous solution and sterile solid waste. Theextent of digestion or degradation of the waste matter may be increasedby treating the waste under pressures above one atmosphere. Aftercooling, the post-digestion end product may then be directly disposed ofthrough conventional disposal means, such as a sanitary sewer orlandfill, or even used as a fertilizing agent in land use applications.If preferred, the post-digestion stage may also include rinsing orflushing of the resultant waste product and the interior of the vessel.The system and method of this invention also substantially reduce theamount of post-digestion solid waste to be disposed of.

The inventors herein have determined that complete digestion (time vs.temperature curves) may be determined by measuring the rate ofproduction of amino acids as the digestion process proceeds. When thatprocess reaches an asymptote, digestion is considered complete.

In operation, when the operator is ready to dispose of the waste matter,such as animal carcasses or remains for example, the waste matter isplaced within a holding container that is then placed within theinterior of the vessel. The lid of the vessel is then secured by way ofconventional lid clamps. The load of waste matter placed in the vesselfor digestion should be at least 10% of the capacity of the vessel (byweight) but not more than 40% of the total weight of the capacity of thevessel. The digestion cycle is then initiated, ultimately resulting inthe waste matter being completely immersed in the highly basic solvent.

For the purposes of this application, a “highly basic solvent” mayinclude a 1-2 molar (M) aqueous solution of an alkali metal hydroxide oran alkaline earth metal hydroxide. Preferably, this solvent should havea pH of at least above 13, preferably in the range of 13 to 14. Anaqueous solution of sodium hydroxide (NaOH—also commonly known as sodiumhydrate) or potassium hydroxide (KOH—also commonly known as causticpotash or potassium hydrate) is preferred. While an aqueous solution ofNaOH or KOH is preferred, solutions containing calcium oxide (CaO—alsocommonly known as burnt lime, calx or caustic lime), ammonium hydroxide(NH₄OH—also commonly known as aqua ammonia) or magnesium hydroxide arealso suitable. An example of a suitable highly basic solvent may consistof a 0.1 M to 2.5 M solution of NaOH in water, or approximately 0.4%-10% sodium hydroxide (by weight) in water.

During digestion, the hydrolyzable material should be immersed in asufficient amount of solvent such that the material may be digested. Oneratio assuring excess base to carry out the digestion of the wastematter to completion, particularly animal tissue, is a 1:10 ratio ofalkali metal hydroxide to wet tissue weight. A further expression ofthis ratio is 40 kilograms of NaOH dissolved in 900 liters of wateradded to 100 kilograms dry weight protein or 40 kilograms of NaOH in 500L H₂O added to 500 kilograms fresh or frozen waste matter by weight.These ratios are given only as instruction as to how to conduct themethod and operate the system stated herein and not to limit the natureor scope of the invention; one using the system and method describedherein may find ratios more economical and exact as the invention ispracticed. In order to assure degradation of all infectious wastes,including prokaryotes, the highly basic solvent should be heated to atemperature of at least 100° C., and preferably 110° C. to 150° C.

It is preferable to allow the reaction to proceed in a closed reactionvessel after the waste matter has been immersed within the solvent.Reducing the amount of CO₂ available to the reaction is beneficial inorder to maintain the ideal rate and stoichiometry of the reaction. Thismay be done by simply removing or limiting any contact that the highlybasic solvent has with the environment.

In the event the reaction between the waste matter such as an animalcarcass and the highly basic solvent were allowed to proceed at itsnatural rate, it may take an impractical amount of time. Therefore, itis advantageous to increase the reaction rate beyond its naturalprogression. One way to increase the speed of the reaction process is toheat the solvent, preferably to temperatures of 110° C. to 150° C.Conducting the reaction in a sealed vessel under increased atmosphericpressure also reduces the reaction time needed to digest the animaltissue. A preferred mode includes heating the solvent to a temperatureof about 150° C. for a duration of about three (3) hours at a pressureof about 2.8 atmospheres. It has been found that the basic rule ofthermodynamics or the “Q10 Rule” applies to this invention as well inthat for every 10 degrees Celsius rise in temperature, the reaction ratefor the chemical reaction taking place within the closed vesselincreases two-fold, thereby resulting in the digestion time beingreduced by approximately 50%. Such phenomenon is based on the Arrheniusequation. In the present invention, the following minimum digestiontimes and automated programmed cycle times have been found to beeffective at certain predetermined temperatures: TABLE ONE MinimumProgrammed Temperature ° C. (° F.) Digestion Time Cycle Time 100 (212) 16 hours N/A 110 (230)   8 hours 16 hours  120 (248)   4 hours 12hours  130 (266)   2 hours 8 hours 140 (284)   1 hour 5 hours 150 (300) .5 hour 3 hours

Furthermore, detergents to a concentration of up to 1% to the solvent,examples being sodium lauryl sulfate or deoxycholate, may also be addedto increase the rate of digestion, if desired. It should also be notedthat addition of detergents to the solvent also has the added advantageof dispersing nonsaponifiable lipids, and aiding in the sterilization ofbiological materials.

Ultimately, the reaction rate will depend on specific variables such as:the temperature of the solvent, pressure in the reaction vessel, thenature and volume of the waste matter, i.e., the physical size of thecarcasses or waste tissue, and the ratio of waste matter to the volumeof the highly basic solvent. As the reaction rate will vary, the timethat the waste matter must remain immersed in the solvent will alsovary. However, regardless of the reaction rate, the waste matter shouldremain completely immersed within the solvent until solubilized andhydrolyzed. Allowing the waste matter to remain within the solvent untildigestion is achieved will also help produce a more sterile solution.

Once the waste matter such as animal tissue has been digested, two typesof solid debris often remain. The first type of debris consists ofrubber, plastic, or cellulosic materials that the lab animal may haveingested, as well as debris remaining from experimental or surgicalprocedures, such as surgical clips, sutures, glass, and bits of plasticor paper. Solid items such as these never incorporate the radioactiveisotopes. Once sterilized, such solid items are also not consideredbiomedical waste in most jurisdictions. This type of debris may often besimply disposed of as ordinary sterile solid waste upon being isolatedfrom the solution and washed.

The second type of solid debris remaining undissolved includes inorganicportions of the animal's skeletal structure and teeth. Unless aradioisotope capable of incorporation into the inorganic portion ofbones and teeth is used, the inorganic component of the skeletal remainswill not contain the radioactive isotope and may be disposed of as solidsterile waste. The skeletal remains, when removed from the solvent andwashed, are extremely friable.

After the biological waste matter has been digested within the solventand the solid debris removed, the solution may comprise a dilutedconcentration of radioactive isotopes that meet the MPC requirementsunder the federal regulations, as well as an alkaline mixture of alkaimetal salts of amino acids and peptides, sugar acids, nucleotides, smallpeptides, fatty acids from lipids, phosphates from lipid and nucleicacid breakdown, soluble calcium salts, pigments, sugars, sugar alcohols,hydrocarbons, and inorganic acids derived from the electrolytes normallywithin solution in body fluids. These by-products are identical to thosereleased in vast amounts from cooking leftovers and waste from allcommercial and household kitchens. Thus, the solution contains compoundsthat are non-toxic and are biodegradable by bacteria or fungi found insoil and sewage treatment systems, and possibly a very dilute amount ofradioactive solute.

Because the solution at the end of the digestion cycle contains onlynon-toxic biodegradable materials and the water released from the animaltissue, further dilution of the solution may not be required for safedisposal. Further dilution to reduce the alkalinity of the solution willbe accomplished, however, by the rinsing of the vessel and the inorganicremains with excess water, by the temperature regulating co-flush forthe effluent, and the general daily effluent volume of the site,institution, or company. (Deliberate dilution of soluble radioactivewaste is usually not permitted by the applicable local, state andfederal regulations.) At this stage, however, the concentration ofradioisotope in the solution should be well within the level that may besafely released to a sanitary sewer.

This sterile, neutral, aqueous solution that contains the breakdownproducts of cells and tissues, and may contain remnants ofradioisotopically labeled solutes may be safely disposed of utilizingmethods commonly used to dispose of everyday nontoxic and biodegradablesubstances. It is entirely safe to dispose of this solution usingdisposal means such as sanitary sewage systems and other disposal meansappropriate for the disposal of these simple biodegradable compounds.

Now turning to FIG. 1, a preferred system 10 for carrying out theinvention is shown schematically, comprising a closed reaction chamberor vessel 12 capable of containing the solvent solution and the wastematter such as the animal tissue or carcass or regulated medical waste.A portion of vessel 12 is defined by a double-walled structure forpurposes discussed below. Naturally, the vessel must be constructed frommaterial capable of withstanding the pH levels, temperatures, andpressures employed in this invention. One such suitable material isstainless steel. Vessel 12 must also be capable of being closed in anair tight fashion to provide the necessary environment within the vesselinterior 14 for the controlled alkaline hydrolysis cycle to be carriedout to completion. Thus, the lid or cover 16 of the vessel 12 must becapable of being closed tightly, pressure and air tight, to withstandthe temperatures and pressures of the digestion cycle and prevent theinadvertent introduction of atmosphere (particularly carbon dioxide)into the vessel interior or, more importantly, prevent the escape orinadvertent exhausting of the contents of the vessel interior toatmosphere. Such closure of the vessel may be achieved by conventionallid clamps well known in the industry (not shown).

The system and method carried out by this invention are controlled by aconventional programmable logic controller (PLC) means (not shown)defined by a programmable multi-loop machine controller, computerizedfor automated operation. Such control means preferably includes aninformation screen, a disk drive for the automation program software,and a keyboard for alternative manual input or operation.

System 10 further includes a weight transducer 18 (shown schematically)coupled to one or more of the legs of the vessel 12 for determining theweight of the waste matter received within the vessel and for generatingan output signal indicating such weight data. The transducer is presetsuch that the weight of the vessel without contents equals zero weight.The contents weight data is then inputted to the PLC control means for,based on the weight output data, determining the appropriate amounts ofwater and solvent to introduce into the interior of the vessel,utilizing a water supply 20, via conduit 20 a, and a spray ball ornozzle 20e located within the vessel interior, and solvent supply 22,via solvent loop conduit 24 and pump 26. Solvent is injected into theinterior of vessel 12 via injector means 28, which are shownschematically in FIG. 1 and in more detail in FIGS. 5A through 5D.Injector means 28 mixes and agitates the contents of the vessel interior14 and enhances the interaction between the highly basic solvent and thewaste matter being digested by directing the jet flow of the solventsolution upwardly at the bottom 62 of the container 60 (see FIG. 5A) tokeep the vessel contents moving and to prevent waste matter fromaccumulating at the bottom of container 60 and not mixing thoroughlywith the solvent. By doing so, the agitating injector means alsoshortens the digestion cycle time.

It should be appreciated that this invention is not limited to theagitating injector means described and shown herein but contemplates anymeans that introduces the solvent into the interior of the vessel. Themere introduction of solvent into the vessel will “mix” the alkali-watersolution with the waste matter. Introducing heat also induces mixing.Moreover, agitation of the contents may be achieved by various means,including external mechanisms coupled to the vessel, such as rocking orshaking assembly that physically moves the vessel. All such alternativemeans of mixing or agitating the vessel contents are contemplated bythis invention.

As noted above, the preferred process requires that the solvent solutionbe heated in order to accelerate the digestion process to completelydissolve the animal tissue, carcasses, or medical waste. To that end,further included in system 10 is a heating means preferably defined by astainless steel steam jacket 30 arranged circumferentially about thevertical sides and base of vessel 12 for heating the interior of thevessel to a first predetermined temperature level after the introductionof water and solvent into the vessel interior 14. Heated water or steamis circulated between the walls of the double walled vessel 12. Whilethe steam jacket defines a preferred embodiment, any heating meanscommonly known and used for heating solutions could be utilized in thisinvention. Steam is supplied to jacket 30 by a steam supply 32 andconduit 32 a provided with a cut-off valve 32 b and a regulating valve32 c. The system further includes a vent 34, which is disposed in theopen state upon initiation of the cycle and thereafter closed by PLCcontrol means when the temperature within the vessel reaches apredetermined first temperature. The temperature within the vessel 12 isgauged by a vessel thermocouple 36 a, while the pressure within thevessel is gauged by a PSI transducer 38. The temperature within thesolvent loop is gauged by a loop thermocouple 36 b.

In the preferred embodiment, an eductor apparatus 40 is utilized forcreating a vacuum within the vessel interior 14. When vent 34 is openand flushing water is admitted to the eductor by the water supply 20 viaconduit 20 b, the action of the eductor draws the air and any odorousgas from within the interior of the vessel through conduit 34 a,whereupon the air and odorous gas is eventually entrapped with theflushing water at eductor 40 to, in turn, be removed from the system viadrain conduit 42 a to sanitary drain 42. The temperature of the fluid atthe drain may be gauged by a thermocouple 44 to monitor the effluenttemperature prior to disposal in a sanitary sewer system. Thevacuum-creating eductor substantially reduces the odorous gases that mayescape from rotting carcasses while the vessel is filling, before thevent valve 34 is closed.

In cycle, once the contents of the vessel are drained after thedigestion cycle (heating and cooling), the interior of the vessel isrinsed with cold water via sprayball 20 e with the drain 41 open. Aftera few minutes, the drain 41 is closed to allow the vessel to begin tofill with water. Once the vessel is filled to the point where the wastematter is covered, the contents are then agitated by injecting the watersolution through injector means 28 for a few minutes to increase therinsing effect. Drain 41 is then re-opened and the liquid contents ofthe vessel are allowed to drain. Thereafter, if desired or necessary,the drain 41 is closed for a second time and the vessel is allowed toagain fill with water. Heat may then be applied again to the vessel toheat the liquid within the vessel to approximately 105° C. (190° F.),whereupon a reverse ion exchange is initiated. The time and temperatureused in this post-digestion heating stage may vary.

To balance or control the vacuum being created within the vessel duringthe post-digestion cooling cycle and to prevent the vacuum from impedingthe draining of the vessel, a vacuum balancing device 46 shown anddiscussed below in relation to FIGS. 4A-4C is provided that selectivelyadmits ambient air to the vessel interior when the internal vacuumpressure reaches or exceeds the threshold pressure of the vacuumbalancer 46. While the vacuum balancer shown and discussed herein is ofa unique design, any vacuum balancing device that will not leak fluid orcollect condensed fluid may be suitable for the effective operation ofthis invention.

Referring now to FIG. 4A, vacuum balancer 46 is shown in detailcomprising a vacuum clamp 47, a vacuum plug 48, an annular end cap 49, avacuum gasket 50, an O-ring 51, a flat washer 52, a socket head capscrew 53, an upper ferrule portion 54, a lower ferrule portion 55, aspring 56 and a thermometer cap 57. In its closed state as shown in FIG.4C, spring 56 urges the cap screw 53, washer 52 and the vacuum plug 48upwardly such that O-ring 51 abuttingly engages the vacuum gasket 50,thereby preventing any air from passing therethrough. When the internalvacuum pressure within vessel 12 reaches a certain point, it willovercome the force of the spring 56, thereby allowing the plug 48 tomove downwardly causing O-ring 51 to disengage from the gasket 50, asshown in FIG. 4B, to admit ambient air into the vessel interior whilethe eductor 40 draws air out of the vessel interior.

The preferred system further includes a permeable container capable ofholding the waste tissue or remains or medical waste within the vesselinterior 14 during the digestion cycle to completely immerse the wastetissue within the solvent solution. As shown in FIGS. 3A-3C, such acontainer preferably includes a cylindrical article 60 defined by asteel mesh screen 62 having an upper rim portion 64, a lower rim portion66, and a lid 68 to enclose the waste tissue within the container 60.(While the preferred shape of the container is cylindrical, othernon-cylindrical shapes are suitable and should be considered as beingwithin the scope of this invention.) Attached to the lid 68 ispreferably a handle 68 a. As shown in FIGS. 3B and 3C, both the lid 68and the bottom of the container include the stainless steel mesh 62,which is preferably constructed from stainless steel screen mesh havingone-eighth (⅛) to one-quarter (¼) inch screen mesh. The lid 68 may bereleasably secured to the body 61 of the container via conventionalmeans. Handle 68 a may be equipped with an eyelet-like portion 68 b toreceive attachment means for lowering and raising the container into andout of the vessel interior. When the waste tissue is digested, thepermeable container 60 may be hoisted out of the vessel 12, or removedout of another port arranged in the side of the vessel 12 during a“clean side” removal as discussed below, thereby removing the undigestedsolid debris remaining within the container 60. The height “h” (FIG. 3A)and diameter “d” (FIG. 3C) of the container may be varied to accommodatevarying amounts of waste tissue or carcasses or animals of varyingsizes, or of medical waste of varying volume or quantity. For the largercontainers, it may be necessary to employ a mechanical hoist system tolower the heavier or more voluminous loads of carcasses of largeranimals or larger quantities of medical waste into the vessel interior.

As noted above, the preferred embodiment includes agitating injectormeans 28 shown in FIGS. 5A-5D to accelerate the reaction rate betweenthe solvent solution and the waste tissue by keeping the solvent inmotion while the reaction is occurring. One such means is accomplishedby circulating the solvent via loop 24 and pump 26 (FIG. 1) andintroducing the solvent into the interior of the vessel by injecting itvia multiple jet ports at varying angles generally aimed at the bottomof the holding container 60 (see FIG. 5A). Such an arrangement keeps thesolvent moving within the vessel interior, as well as keeping wastematter from accumulating on the bottom of the container 60, which canresult in the prolonging or slowing of the digestion process. Agitatinginjector means 28 preferably comprise a plurality of concentric flowreducers or nozzles 28 a coupled to a respective elbow members 28 b,which in turn are coupled to respective tube members 28 c, which finallyare coupled to respective cross member 28 ds. Each cross member 28 d isconnected to a screw-coupling member 28 e for affixing the injectormeans to the upper end of the inflow conduit 24 a. In a preferredembodiment, the opposing nozzles 29 a are disposed at an included angleA of about 22.5 degrees (FIG. 5C), while opposing nozzles 29 b aredisposed at an included angle B of about 45 degrees (FIG. 5D), toenhance the agitation and mixing action of the injectors to facilitatethe digestion reaction.

As shown in FIG. 5A, the inflow conduit 24 a delivering solvent toinjector 28 extends into and, in a coaxial fashion, extends upwardlythrough the outflow conduit 24 b. Inflow conduit 24 a is smaller indiameter than outflow conduit 24 b such that the aqueous interiorcontents of the vessel 12 may drain downwardly into outflow conduit 24 bas shown by the reference arrows “a” in FIG. 5A. Outflow conduit 24 bcarries the solvent back to the solvent loop 24 and pump 26 (see FIG. 1)and when necessary, through drain valve 41 to the sanitary drain 42. Itwill be understood by those skilled in the art that the points ofconnection “b” shown in FIG. 5A must be sufficiently tight and withstandthe highly basic, high-temperature, and high-pressure environment. Itshould be further understood the injector means may include separateinjector nozzles disposed in fixed arrangements about the interior ofthe vessel to direct solvent at the waste matter. Such a configurationis useful in larger applications involving large diameter containers andlarge-volume waste matter. Such separate fixed injections may beutilized in lieu of or in addition to the injector assembly 28 shown anddescribed herein.

FIG. 2 presents a flowchart depicting the cycle process of thisinvention. In operation, the waste matter is weighed and the weight andwater and solvent ratios automatically determined by the PLC controlmeans (box a). The appropriate amount of water (box b) and solvent (boxc) is then introduced into the interior of the vessel based on theweight calculations made by the PLC control means. Water is added at therate of 60% water to 40% tissue by weight. The alkali is added at thepredetermined concentration based on the tissue weight. This istypically equivalent to a solution of 50% NaOH added by weight at aratio of 15 to 20% of the total tissue weight. The heating means 30(FIG. 1) then heats the vessel interior (box d) to the digestion cycletemperature while closing the vent 34 (box e). System 10 then maintainsthat elevated temperature for a predetermined duration (box f) ascalculated by the PLC control means based on the weight of the wastematter placed in the vessel for digestion. The system typicallymaintains the digestion temperature at about 150° C. (302° F.) for about3 hours, or if operated at a lower temperature, for a time at leastdouble the digestion time for that temperature (doubling the minimumdigestion time for each 10 degrees Celsius decrease in temperature) inaccordance with the thermodynamics equation discussed above.

Next, the system goes into the cooling cycle after digestion whereuponcooling water is admitted to the steam jacket interior 30 from watersupply 20 (FIG. 1) via conduit 20 c to lower the temperature of thevessel interior (box g). This continues until the internal pressurewithin the vessel reaches about atmospheric pressure (101.3kilopascals/14.7 pounds per square inch (PSI)), shown as a reading ofzero on the pressure gauge or transducer, which measures pressure above1.0 atmosphere. Once the system is cooled sufficiently, the vessel isdrained to the sewer (sanitary drain 42) by the control means openingthe vent 34 (box h) and drain 41 (box i) to drain the liquid contentsfrom within the vessel interior down to a predetermined point, at whichpoint drain 41 is closed (box j) while flushing water is continued to beintroduced to flush the vessel interior (box k) until the interior ispreferably about half full. At that point in the cycle, the vesselinterior is sprayed with rinsing liquid and the contents are circulatedthrough the injectors 28 for a predetermined time before the drain isagain opened to rinse away any residual materials remaining within theinterior of the vessel (boxes l and m). The drain is then closed again(box n) and the vessel partially filled again and a final heated rinsecycle is then carried out (boxes o, p, and q). At this stage, thedigestion and cooling cycle are complete and the vessel may be openedand the waste holding container removed and emptied. The empty containeris then replaced within the vessel interior rendering the system readyfor subsequent operation.

This invention also presents a method for digesting or neutralizingwaste matter comprising organic tissue or infectious, biohazardous,hazardous, or radioactive agents, by subjecting the waste matter to acontrolled alkaline hydrolysis cycle and generating a sterile resultantsuitable for conventional sanitary disposal. The preferred methodcompromises the steps of:

-   -   (a) providing a closed reaction vessel 12 coupled to a        heating-cooling means;    -   (b) receiving the waste matter within the closed reaction vessel        12;    -   (c) determining the weight of the waste matter received within        said vessel and generating weight output data by way of a weight        transducer 18 coupled to the vessel 12;    -   (d) controlling the operation of the system, including receiving        and considering the weight output data generated by the weight        determining transducer 18 and determining the appropriate        amounts of water and solvent to introduce into the interior of        the vessel 12;    -   (e) after determining the appropriate amounts of water and        solvent to introduce into the interior of the vessel, initiating        a vacuum on the vent of the vessel to remove odors while        introducing water within the vessel interior in an amount        determined by the PLC controller via water supply 20 and conduit        20 a based on the weight output data, and introducing the highly        basic solvent into the interior of the vessel in an amount        determined by the PLC controller based on the weight output        data;    -   (f) heating the interior of the vessel to a first predetermined        temperature level by way of the heating means (steam jacket 30)        after the introduction of water and alkali solution into the        interior of the vessel;    -   (g) mixing or agitating the contents of the vessel to enhance        the interaction between the solvent and the tissue by way of        agitating injector means 28;    -   (h) continuing to vent the interior of the vessel by way of vent        34 upon initiation of the digestion cycle and closing the vent        when the temperature within the vessel reaches a first        predetermined temperature;    -   (i) heating the vessel interior to the digestion cycle        temperature and maintaining that temperature for a predetermined        duration;    -   (j) cooling the interior of the vessel after the digestion cycle        has run by introducing cooling water from supply 20 to heating        means 30;    -   (k) operating eductor 40 and opening vent 34, thereby creating a        vacuum, to remove any odorous gases from within the vessel        throughout the remainder of the post-digestion process;    -   (l) balancing the vacuum created by eductor 40, via vacuum        balancer 46, to prevent such vacuum from interfering with the        draining of the vessel by selectively admitting ambient air into        the vessel interior during the remainder of the post-digestion        process;    -   (m) opening drain 41 to drain the digested liquid portion of the        vessel contents and initiating a spray rinse by opening line 20        a to remove any remnants of the solvent solution from the solid        waste remains within the vessel interior;    -   (n) closing drain 41 while maintaining spray line 20 a open to        continue the spray rinse via sprayball 20 e, and opening water        line 20 d to refill the vessel with water to approximately 15.24        cm (6 in.) above the bottom of the digestion container 60 and        restarting the pump 26 to recirculate the rinse solution        throughout the solid waste remains via loop 24 for a        predetermined time to allow for additional rinsing of the solid        waste remains;    -   (o) opening drain 41 to drain the rinsing liquid portion of the        vessel contents;    -   (p) initiating another spray rinse by opening line 20 a to        further remove any remaining solvent rinse solution from the        solid remains;    -   (q) closing drain 41 while maintaining spray line 20 a open and        opening water line 20 d to, again, refill the vessel with water        to approximately 15.24 cm (6 in.) above the bottom of the        digestion container 60 and restarting the pump 26 to recirculate        a rinse solution throughout the solid waste remains for a second        time;    -   (r) heating the second rinse solution to a predetermined        temperature and recirculating the second heated rinse solution        for a predetermined time to allow the solution to remove any        entrained digestion solution from the solid waste remains;    -   (s) opening drain 41 to allow the second heated rinsing solution        to drain;    -   (t) opening spray line 20 a for a final rinse of the vessel        interior and solid waste remains while maintaining drain 41        open; and    -   (u) closing spray line 20 a to discontinue the rinse and        allowing the liquid contents of the vessel to drain; and    -   (v) finally, opening the lid 16 of the vessel and removing the        waste remains from the primary opening for disposal in a        sanitary landfill or for usage as solid fertilizer material.

As mentioned above, an additional feature of the closed vessel is toallow the solid waste remains to be removed from a secondary opening(not shown) arranged on the vertical side of the vessel. This featureallows the vessel to be positioned in such a configuration that theprimary opening may be located within a contaminated portion of thefacility, while the remaining portions of the system are located withina clean portion of the facility. This would allow contaminated materialsto be processed and sterilized, then for the sterile solid waste remainsto be removed from the secondary opening as sterile remains into a cleanarea for final disposal. Thereafter, the secondary opening would besealed prior to the opening of the primary opening for the loading ofwaste for another processing cycle. Such a configuration is referred toas “dirty side feed/clean side removal.” Such an embodiment would alterstep (u) above to read as follows:

-   -   (u) finally, opening the vessel and removing the solid waste        remains from the secondary opening for disposal in a sanitary        landfill or for usage as solid fertilizer material, then closing        and re-sealing the secondary opening prior to opening the        primary opening for the loading of new waste material for a        subsequent cycle, wherein the dirty side door or lid and the        clean side door or lid are electrically interlocked to assure        compliance with regulations and prevent contamination of the        clean side.

Finally, set forth below is an example of the system of this inventionand its method of operation in use.

EXAMPLE ONE

Prior to filling the vessel with, for example, animal carcassescontaining infectious or hazardous agents, the lid of the vessel isclosed in order to “zero” the load scale. The lid is then opened and thevessel filled with waste matter to the desired volume. Preferably, theload should be at least 20% of the vessel's capacity (by weight) but notmore than the weight capacity of the vessel, in which case the systemwill not operate and the excess weight must be removed. The vessel lidis then closed and secured. The PLC controller is then activated toinitiate the digestion process by first determining the weight of thewaste matter within the vessel. The digestion cycle is then initiatedwhereby waste is preferably added at the rate of 60% waste to 40% tissueby weight, alkali is added at the predetermined concentration based onthe tissue weight. Such concentration is normally equivalent to asolution of 50% HaOH added by weight at a ratio of 15 to 20% of thetotal tissue weight.

The heating step is then initiated to raise the temperature of theinterior of the vessel to the predetermined first digestive cycletemperature for a predetermined duration to completely digest thecarcasses. In a preferred mode, the cycle holds the digestiontemperature to at least 110° C., preferably about 130° C., and mostpreferred about 150° C. At 150° C., the digestion cycle is normallyabout 3 hours in duration.

Once the digestive cycle is complete, the PLC control means initiatesthe cooling cycle, utilizing cold water flushed through the sleevejacket 30 of the vessel. Once the vessel has cooled sufficiently, thevessel is drained to the sewer, then partially refilled with cold waterand the interior rinsed. The vessel is then drained again, partiallyrefilled again and this second rinse solution heated if desired. Afterthis hot rinse, the vessel is then drained and it contents sprayed witha final spray rinse. The cooling cycle is then complete and the systemshuts down while the drain is opened to empty completely the interior ofthe vessel.

If the operator is present at the completion of the cooling cycle, thevessel may at that point be opened and the waste-carrying basket removedand emptied. The basket is then replaced, making the system ready for anew cycle. In the event, however, the operator is not present when thecooling cycle is complete, when the cycle runs at night for example, theoperator should initiate the rinse cycle for a short duration,preferably about 30 seconds. After the final spray is complete, thevessel may be opened and the waste safely disposed of

Although the invention has been described with a preferred embodiment,those skilled in the art will understand that modifications andvariations may be made without departing from the scope of theinventions as set forth in the following claims. Such modifications andvariations are considered to be within the purview and scope of theappended claims.

1. A system for digesting or neutralizing biologically hazardousmaterials by subjecting them to a controlled alkaline hydrolysis cycleto generate a sterile resultant suitable for conventional sanitary orland application disposal, said biologically hazardous materialscomprising organic tissue, biohazardous or hazardous agents andregulated medical waste, said system comprising: (a) means for receivingthe biologically hazardous materials, said receiving means being capableof forming a closed reaction vessel; (b) means for determining theweight of the biologically hazardous materials received within saidvessel and for generating weight output data; (c) means for controllingthe operation of the system, for receiving and considering the weightoutput data generated by said weight determining means in determiningthe appropriate amounts of water and alkali compound to introduce intothe interior of the vessel; (d) means for introducing water within theinterior of said vessel in an amount determined by said control meansbased on the weight output data; (e) means for introducing an alkalicompound within the interior of said vessel in an amount determined bysaid control means based on the weight output data; and (f) means forheating the interior of the vessel to a first predetermined temperaturelevel after the introduction of water and alkali compound into theinterior of the vessel for a duration sufficient to produce a safelydisposable resultant.
 2. The system as in claim 1 further comprising:(g) means for mixing the contents of the vessel to enhance theinteraction between the alkali compound and the biologically hazardousmaterials.
 3. The system as in claim 2 further comprising: (h) means forventing the interior of the vessel, said venting means being operable tobe in the open state upon initiation of the cycle and to be closed bysaid controlling means when the temperature within the vessel reaches afirst predetermined level; (i) means for cooling the interior of thevessel after the alkaline hydrolysis cycle has run by introducing acoolant to the vessel; (j) means for creating a vacuum within theinterior of said vessel; (k) means for balancing the vacuum createdinterior by said vacuum means within the vessel to prevent the vacuumexisting within said vessel from exceeding a predetermined level duringoperation of the system by selectively admitting ambient air into thevessel interior during cycle; and (l) means to initiate a spray rinse torinse the digestive solution from the solid remains.
 4. The system as inclaim 3 further comprising: (m) means for draining the contents from theinterior of said vessel, said heating means being adapted to heat theinterior of the vessel to a second predetermined cycle temperature for apredetermined duration, after which point said cooling means lowers thetemperature of the vessel interior to a third predetermined temperaturewhereby the internal pressure within the vessel reaches about zeropounds per square inch, after which point said water introduction meansflushes the interior of the vessel and said control means opens saidventing means and said draining means drain the contents from within thevessel interior down to a predetermined level, after which point saiddrain means closes while the water introduction means continues to flushthe vessel interior until the interior is partially full, after whichpoint the vessel interior is sprayed with a final rinsing liquid torinse away through the drain means any compounds remaining within theinterior of the vessel.
 5. The system as in claim 3 wherein said rinsingliquid comprises water.
 6. The system as in claim 3 wherein said coolantcomprises water.
 7. The system as in claim 1 wherein said biologicallyhazardous materials further comprises human and animal tissue, animalcarcass, human cadaver, pathological waste, regulated medical waste orradioactively contaminated tissue.
 8. The system as in claim 1 whereinbiologically hazardous materials comprises embalming agents, toxiccontaminants, pathogens, antineoplastic agents or microbial agents. 9.The system as in claim 8 wherein said embalming agents includeformaldehyde, glutaraldehyde and phenol.
 10. The system as in claim 1wherein said alkali compound comprises sodium hydroxide (NaOH).
 11. Thesystem as in claim 1 wherein said alkali compound comprises potassiumhydroxide, calcium oxide, ammonium hydroxide or magnesium hydroxide. 12.The system as in claim 1 wherein said weight determining means comprisesweight transducers coupled to the vessel.
 13. The system as in claim 1further comprising thermocouple means for monitoring the temperaturewithin the interior of the vessel.
 14. The system as in claim 1 whereinsaid alkali and water introduction means comprises a loop supply systemincluding conduit means, a pump for pumping the alkaline compound from asupply source to the vessel via the conduit means to be introducedwithin the vessel interior by way of said agitation means, and athermocouple means to monitor loop temperature.
 15. A method fordigesting or neutralizing waste matter, said waste matter includinghazardous or biohazardous agents or regulated medical waste containinginfectious agents, said infectious agents comprising hydrolyzablematerial, said method comprising the steps of: (a) providing a highlybasic solvent; (b) immersing said waste matter into said highly basicsolvent; and (c) heating said highly basic solvent and said immersedwaste matter to a temperature of at least 110° C. and at a pressuregreater than about 2.8 atmospheres and for a time sufficient to digestsaid hydrolyzable material, whereby a sterile solution comprisingnon-toxic biodegradable materials and containing sterile solid wastefree of said infectious agents is produced.
 16. The method of claim 15wherein said highly basic solvent has a pH in the range of about 13 toabout
 14. 17. The method of claim 15 wherein said highly basic solventcomprises a mixture of water and an alkali metal hydroxide or alkalineearth-metal hydroxide.
 18. The method of claim 15 wherein said heatingstep (c) is performed at a temperature of at least 130° C.
 19. Themethod of claim 15 wherein said heating step (c) is performed at atemperature of about 150° C.
 20. The method of claim 12 furthercomprising agitating, circulating, or stirring the highly basic solventin step (c).
 21. A method for digesting or neutralizing waste matter,said waste matter including hazardous or biohazardous agents orregulated medical waste containing infectious agents, said infectiousagents comprising hydrolyzable material, said method comprising thesteps of: (a) providing a highly basic solvent; (b) immersing said wastematter into said highly basic solvent; and (c) heating said highly basicsolvent and said immersed waste matter to a temperature of at least 130°C. and for a time sufficient to digest said hydrolyzable material,whereby a sterile solution comprising non-toxic biodegradable materialsand containing sterile solid waste free of said infectious agents isproduced.
 22. The method of claim 21 wherein said heating step (c) isperformed at a pressure of at least about 2.8 atmospheres.
 23. A methodfor digesting or neutralizing undesirable materials such as organictissue or hazardous or biohazardous agents or regulated medical waste bysubjecting them to an alkaline hydrolysis cycle and generating a sterileresultant suitable for conventional sanitary disposal or landapplication, said method compromising the steps of: (a) providing aclosed reaction vessel coupled to a heating-cooling means; (b) receivingthe undesirable materials within said vessel; (c) determining the weightof the undesirable materials received within said vessel and generatingweight output data; (d) controlling the operation of the system,including considering the weight output data and determining theappropriate amounts of water and alkaline compound to introduce into theinterior of the vessel; (e) after step (d), introducing an alkalicompound within the interior of said vessel in an amount based on theweight output data; (f) after step (d), introducing water within theinterior of said vessel in an amount based on the weight output data;and (g) after steps (e) and (f), heating the vessel interior to a firsttemperature for a sufficient duration to produce a safely disposableresultant.
 24. The method as in claim 23 further comprising the stepsof: (h) during steps (e) and (f), initiating a vacuum within the vent ofthe vessel to remove waste odors while filling the vessel; (i) duringsteps (e) and (f), mixing the contents of the vessel to enhance theinteraction between the alkali compound and the undesirable materials;(j) after step (g), cooling the interior of the vessel to apredetermined temperature after the digestion cycle has run; (k) afterstep (j), venting the interior of the vessel upon the vessel reaching apredetermined second temperature and the pressure reaching about one (l)atmosphere; (l) during step (k), creating a vacuum within the interiorof the vessel to remove odor from therewithin; (m) during step (k),balancing the vacuum so created to prevent said vacuum from interferingwith the draining of the vessel; (n) after step (m), draining the liquidsolution portion of the vessel contents from the interior of the vessel;and (o) after step (n), rinsing the interior of the vessel to remove anyremaining solution residue from any solid remains of the undesirablematerials.
 25. The method as in claim 24 further comprising the stepsof: (p) during step (o), closing the drain while continuing the rinsingand partially re-filling the vessel and agitating the rinse solutionthroughout any solid waste remains; (q) after step (p), circulating therinse solution for a predetermined duration to allow the rinse solutionto remove any entrained digestion solution from any solid waste remainsof the undesirable materials; and (r) after step (q), draining therinsing solution from the interior of the vessel.
 26. The method as inclaim 25 further comprising the step of heating the rinse solutionduring steps (p) or (q).
 27. The method as in claim 25 furthercomprising the steps of: (s) after step (r), conducting a subsequentrinse of the interior of the vessel to remove any solid waste remainsfrom the undesirable materials; and (t) during step (s), disposing ofthe resultant effluent by way of conventional means.
 28. The method asin claim 27 further comprising the step of: (u) after step (t), openingthe vessel and removing said solid waste remains for disposal in asanitary landfill or for usage as solid fertilizer.
 29. The method ofclaim 23 wherein said highly basic solvent has a pH of at least about13.
 30. The method of claim 23 wherein said highly basic solventcomprises a mixture of water and an alkali metal hydroxide or alkalineearth-metal hydroxide.
 31. The method of claim 23 wherein said heatingstep (h) is performed at a temperature of at least 110° C.
 32. Themethod of claim 23 wherein said heating step (h) is performed at atemperature of at least 130° C.
 33. The method of claim 23 wherein saidheating step (h) is performed at a temperature of about 150° C.
 34. Themethod of claim 23 wherein said heating step (h) is performed at apressure of at least about 2.8 atmospheres.
 35. The method of claim 19wherein said vessel is coupled to a heating-cooling means, wherein theheating step (i) is carried out by introducing steam to saidheating-cooling means, and wherein the cooling step (j) is carried outby introducing water to said heating-cooling means.
 36. A method fordigesting or neutralizing waste matter, said waste matter includinghazardous or biohazardous agents or regulated medical waste containinginfectious agents, said infectious agents comprising hydrolyzablematerial, said method comprising the steps of: (a) providing a highlybasic solvent; (b) immersing said waste matter into said highly basicsolvent; and (c) heating said highly basic solvent and said immersedwaste matter to a temperature of at least 110° C. and at a pressuregreater than about 2.8 atmospheres and for a time sufficient to digestsaid hydrolyzable material, whereby a sterile solution comprisingnon-toxic biodegradable materials and containing sterile solid wastefree of said infectious agents is produced.
 37. An apparatus fordigesting or neutralizing biologically infectious materials, comprising:(a) a sealable reaction vessel configured to receive infectious wastematerials; (b) a weight transducer operably connected to the reactionvessel, the weight transducer being capable of determining the weight ofthe infectious materials received within the vessel and generating anoutput signal indicating the weight; (c) a controller capable ofreceiving the output signal from the weight transducer, determining theappropriate amounts of water and alkaline solvent, and generating anoutput signal indicating the appropriate amounts of water and alkalinesolvent; (d) an injector capable of receiving the output signal from thecontroller and introducing the appropriate amount of alkaline solvent tothe vessel based on the output signal; and (e) a heater capable ofheating the vessel to a predetermined temperature and maintaining thetemperature for a duration sufficient to substantially digest thebiologically infectious materials.
 38. The apparatus of claim 37,further comprising: (f) an eductor operably connected to the vessel soas to draw gas from the vessel; (g) a vacuum balancing valve operablyconnected to the vessel and capable of selectively admitting ambient airto the vessel when the internal pressure drops below a predeterminedlevel; (h) a water supply conduit operably connected to the vessel andcapable of introducing cooling water to the vessel; and (i) athermocouple operably connected to the vessel and capable of determiningthe temperature of the vessel interior.
 39. The apparatus of claim 38,wherein the eductor valve is further operably connected to the watersupply conduit such that gases vented through the eductor are entrappedin water passing through the water supply conduit.
 40. The apparatus ofclaim 37, wherein the alkaline solvent comprises one or more aqueoussolutions of sodium hydroxide, potassium hydroxide, ammonium hydroxide,magnesium hydroxide, or calcium oxide.